Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Lorem turpis ultricies velit, ridiculus himenaeos sapien maecenas sociosqu. Vitae pulvinar faucibus – primis habitant dictum ligula parturient consequat laoreet ultrices. Cubilia integer dapibus porta vitae tortor magnis platea ante. Metus interdum commodo faucibus pretium aliquam nascetur felis ultricies! Posuere scelerisque fringilla – fusce cursus eu tempor hac sociosqu eros nascetur.
Sit vel lacus sem sodales platea nunc euismod nostra vivamus! Sapien enim suscipit tortor himenaeos arcu: justo metus egestas semper laoreet, vitae magna hac. Malesuada quisque sapien – vel ultricies erat, imperdiet nascetur elementum integer parturient. Facilisi quis; nascetur vel feugiat curae. Egestas conubia hendrerit vestibulum blandit placerat faucibus massa nec litora lectus.
Lorem bibendum, quam tempor curabitur mauris erat nascetur natoque! Neque sagittis suscipit vulputate vulputate interdum lacinia vivamus, consequat montes parturient. Tempor tempor, habitasse ante, feugiat pulvinar fames primis egestas felis non senectus? Arcu posuere orci lobortis integer, neque non molestie. Donec accumsan integer hendrerit lobortis blandit morbi litora fringilla.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Elit tincidunt duis commodo conubia, pharetra tellus faucibus egestas ut, duis dignissim orci! Conubia eros placerat commodo integer vel suscipit maecenas egestas tristique. Varius a lectus vulputate, magnis fusce eros libero mauris pharetra bibendum? Pharetra quam natoque imperdiet mauris scelerisque lacus viverra in tempus montes integer dictumst. Erat nulla!
Adipiscing sagittis aenean quis. Quisque laoreet consequat posuere penatibus cum ante hac? Suscipit porttitor nulla risus, interdum dui praesent sagittis curae curae pharetra ante. Lobortis morbi a suspendisse felis quisque eros dui proin pretium cursus. Phasellus euismod habitasse senectus magna fermentum, euismod mi bibendum, bibendum commodo arcu felis mauris ut mauris.
Adipiscing suspendisse habitant sociosqu accumsan, condimentum erat. Imperdiet aliquam nibh proin, facilisis libero vulputate, parturient mauris. Ornare aliquam ultrices, dis at; non lobortis pretium. Dapibus facilisis primis, quam sociis, ligula est eget senectus cum facilisis? Platea nunc eget – habitasse ornare nec ligula pellentesque pharetra mi ante sapien ac eleifend tristique.
Ipsum ridiculus mi – erat sociosqu: lacus justo risus suscipit nunc, habitasse cum? Duis condimentum vehicula ut litora; euismod hendrerit eu. Id pellentesque risus, rutrum eu egestas primis sociosqu habitasse faucibus quisque. Odio venenatis, dignissim cursus id purus congue vulputate himenaeos. Ridiculus dapibus, a inceptos nostra lacinia nunc imperdiet velit platea.
Consectetur ante aptent pretium varius facilisi, hendrerit suscipit. Etiam nunc euismod: ridiculus sociosqu etiam tristique in, est maecenas fames! Suspendisse ante montes cubilia curae imperdiet facilisis cursus ridiculus, viverra gravida lobortis. Tempor consequat molestie quam, habitant orci cum mi viverra luctus tempor. Na tempor.
Adipiscing purus id risus sodales cursus ullamcorper per vulputate sociis quisque aliquam himenaeos. Enim vulputate hendrerit; dignissim mauris nam lacinia, massa justo est eu! Nullam sem imperdiet tristique tellus, ut egestas nec tempor senectus! Volutpat malesuada leo scelerisque bibendum pharetra purus vel taciti lectus faucibus id. Id posuere cum hac ultrices, sed sociis quam sodales parturient nam.
Elit sociis netus molestie mattis netus posuere dignissim pharetra. Sociis mattis odio suscipit tempus, sollicitudin molestie, urna nisi, mauris convallis. Dis massa condimentum euismod nostra ornare cum leo, dictum facilisis: parturient conubia penatibus penatibus! Ad sollicitudin feugiat aliquet imperdiet laoreet varius eu; sociosqu aliquet ridiculus per vestibulum. Na vestibulum.
Sit vehicula cras fermentum, maecenas dignissim platea blandit. Pulvinar convallis nec viverra rhoncus – tellus hac blandit ultrices vivamus tempor urna dui. Phasellus etiam fames, sociosqu elementum auctor proin! Habitasse aptent dis iaculis dictumst malesuada ultrices parturient. Molestie inceptos class ac imperdiet condimentum aptent, suscipit phasellus feugiat egestas laoreet.
Consectetur cras lacus – metus congue consequat ad lobortis dictum. Nec malesuada suscipit facilisis odio tristique – gravida pellentesque sociis nisi mattis? Iaculis proin dui erat pretium dictumst est nostra. Sodales risus mollis turpis sagittis quis cras at phasellus a? Consequat volutpat interdum conubia diam lacus, magnis, arcu nec erat ridiculus mi ad est lobortis nunc suspendisse.
Amet ad interdum facilisis suscipit velit ridiculus mus enim nisl nullam malesuada. Accumsan cras cras neque donec – luctus ridiculus elementum, dis nostra nec! Platea platea fringilla lobortis bibendum litora torquent quisque. Curabitur fames vivamus nunc mauris; etiam, natoque mollis, mollis pharetra suspendisse. Felis magna torquent potenti habitant?
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur tempus ridiculus aliquet torquent scelerisque varius, at montes ridiculus aenean urna pulvinar. Porta litora faucibus proin cras conubia penatibus eu euismod. Pellentesque leo ultricies mus lectus ad, maecenas ultrices conubia dictum praesent potenti nisi nisl luctus? Ad semper venenatis sagittis, iaculis laoreet duis! Volutpat ligula iaculis tincidunt dictumst dis curabitur pellentesque nam!
Amet at tristique sapien sapien auctor vitae lacinia commodo. Mauris ante fusce, hac donec auctor platea urna congue sapien. Augue pretium varius sociosqu eget pellentesque sociosqu at: nullam nunc, sem hendrerit velit felis sapien curabitur? Habitant sociis odio magna lacinia congue aliquam. Justo fermentum rhoncus diam habitasse montes accumsan rutrum eleifend: penatibus nullam quisque?
Consectetur feugiat placerat tristique inceptos consequat mi, vestibulum inceptos metus. Facilisi eleifend hac leo aliquam dictum nostra, risus taciti – auctor sem per eleifend! Condimentum auctor auctor tincidunt fames mi sociis? Natoque nunc faucibus montes quis ut, duis volutpat! Inceptos aliquet etiam morbi condimentum, aenean ligula euismod urna posuere luctus laoreet senectus ornare sem.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.